Machine of variable linear structure for the formation of tubes

ABSTRACT

The machine for the formation of tubes includes at least, in series with each other, forming stations including pairs of idle rollers which make rototranslational movements of the same amplitude but in opposite directions, and at least one finishing station including four idle rollers having a concave profile with a constant curvature and able to perform rototranslational movements of the same amplitude and direction according to 90° axes. The lower rollers of each forming station have an elliptical profile with a curvature decreasing form the outer edge to the inner edge of the roller. The upper rollers of the first forming station have an elliptical profile with a curvature increasing from the outer edge to the inner edge of the roller; the upper rollers of the forming stations subsequent to the first have a circular profile.

The present invention refers to a machine for the formation of tubes,called “of variable linear structure”, which comprises a plurality offorming stations, placed in series with each other, which progressivelybend a strip of sheet metal to form a tube, followed by at least onefinishing station which further brings together the edges of the bentstrip of sheet metal in view of the final welding.

Machines for forming tubes by means of continuous bending of sheet metalare well known to the art and comprise, in series with each other, aplurality of stations in which the strip of sheet metal is progressivelydeformed by pairs of rollers having matching profiles.

These machines of the prior art have the drawback of making it necessaryto replace the pair of rollers when it is desired (or necessary) tochange the diameter of the tube produced, which leads to more or lesslong machine downtimes which reduce the productivity of the plant.

To overcome this serious drawback, machines for forming tubes by meansof continuous bending of sheet metal have been proposed (such as, forexample, that described in European patent EP 1 393 830 in the name ofthe Applicant) in which the two pairs of rollers with matching profilesbelonging to a station can make rototranslational movements of the sameamplitude but in opposite directions, making it possible to use the samepairs of rollers to produce tubes whose diameter falls within a more orless broad range of values.

Object of the present invention is to realise a machine “of variablelinear structure” for the formation of tubes, which improves theperformance of machines of the type described, for example, by theaforementioned European patent since it allows the range of values ofthe diameter of the tubes to be widened without having to replace thepairs of rollers.

This object is achieved by means of a machine which has thecharacterising features indicated in independent claim 1.

Further advantageous characteristics of the invention form the subjectmatter of the dependent claims.

A machine for continuous formation of tubes realised according to theinvention comprises, in series with each other, forming stations whichprogressively bend a strip of sheet metal and at least one finishingstation which further brings together the edges of the bent strip ofsheet metal in view of the final welding.

Each forming station comprises two pairs of idle forming rollers whichmake rototranslational movements of the same amplitude but in oppositedirections and the at least one finishing station comprises four idleforming rollers able to make movements of the same amplitude anddirection according to 90° axes.

The profile of the lower rollers of each forming station is ellipticalwith a decreasing curvature from the outer edge to the inner edge ofsaid roller, that of the upper rollers of the first forming station iselliptical with an increasing curvature from the outer edge to the inneredge of said roller, that of the upper rollers of the forming stationssubsequent to the first one (hereafter called “second forming stations”)is circular and that of the forming rollers of the at least onefinishing station is concave with a constant curvature.

The radius of the circular profile of the upper rollers of each secondforming station preferably corresponds to the minimum radius ofcurvature of the bent strip of sheet metal in correspondence of saidsecond forming station and the curvature of the concave profile of theforming rollers of the at least one finishing station corresponds to themaximum curvature of the bent strip of sheet metal in correspondence ofsaid finishing station.

A machine according to the invention is called “of variable linearstructure” since (as indicated very diagrammatically in FIGS. 5 and 7)makes it possible to produce tubes of different diameters by changingthe reciprocal positions of the two pairs of rollers and those of eachof the rollers of each pair.

The invention will now be described with reference to purelyexemplifying (and therefore non limiting) embodiments thereofillustrated in the appended figures, wherein:

FIG. 1 shows diagrammatically a perspective view of a machine for theformation of tubes realised according to the invention;

FIG. 2 shows diagrammatically a side view of the machine of FIG. 1;

FIG. 3 shows diagrammatically a front view and an enlarged detail (FIG.3 a) of the first forming station of the machine of FIG. 1;

FIG. 4 shows diagrammatically, enlarged, a pair of forming rollersbelonging to the first forming station of FIG. 3;

FIG. 5 shows diagrammatically, enlarged, the position assumed by the twopairs of forming rollers of the first forming station of FIG. 3 toproduce three tubes of different diameters;

FIG. 6 shows diagrammatically a front view and an enlarged detail (FIG.6 a) of a second forming station of the machine of FIG. 1;

FIG. 7 shows diagrammatically, enlarged, the position assumed by the twopairs of forming rollers of the second forming station of FIG. 6 toproduce the three tubes of different diameters of FIG. 5;

FIG. 8 shows diagrammatically a front view and an enlarged detail (FIG.8 a) of one of the containment stations situated downstream of the firstforming station and of each of the second forming stations;

FIG. 9 shows diagrammatically a front view (FIG. 9 a), a side view (FIG.9 b) sectioned along the plane F-F of FIG. 9 a and an enlarged detail(FIG. 9 c) of a finishing station belonging to the machine of FIG. 1.

In the appended figures corresponding elements will be identified bymeans of the same reference numerals.

FIG. 1 shows diagrammatically a perspective view of a machine 1according to the invention for the formation of tubes 2 which comprises,in series with each other, traction means 13 for the strip of sheetmetal 4 (which enters the machine 1 in the direction of the arrow I), afirst forming station 3, second forming stations 3′, containmentstations 12 (each of which is situated downstream of a forming station),at least one finishing station 5 and at least one welding station (perse known and omitted in FIGS. 1 and 2), from which the tube 2 exits inthe direction of the arrow U.

In the embodiment illustrated in FIGS. 1 and 2 the machine 1 comprisesfive second forming stations 3′, six containment stations 12 (visible inthe side view of FIG. 2) situated downstream of the forming stations (33′) and two finishing stations 5 but, without departing from the scopeof the invention, the number of second forming stations 3′ (and,consequently, that of containment stations 12) and finishing stations 5can vary to meet the particular requirements of a specific machine 1.

The traction means 13 will not be described because they are per seknown. The first forming station 3 will be described with reference toFIGS. 3-5, a second forming station 3′ will be described with referenceto FIGS. 6-7, a containment station 12 will be described with referenceto FIG. 8 and a finishing station 5 will be described with reference toFIG. 9.

FIG. 2 shows diagrammatically a side view of the machine 1 of FIG. 1,which makes it possible to see more clearly the containment stations 12situated downstream of a forming station (3, 3′).

FIG. 3 shows diagrammatically a front view of the first forming station3 of the machine 1, symmetrical with respect to the midline, whichcomprises two vertical uprights 31 which support two horizontaltraverses 32, sliding along the uprights 31; along each traverse 32slide two shoes 33, on each of which is present a pivot 34 which acts asa fulcrum for rotation of a unit 35 that carries one of the formingrollers (8, 8′).

The pivots 34 and the units 35, which can be seen better in FIG. 3A,have not been designated with the corresponding reference numerals inFIG. 3 for the sake of clarity of the graphic representation.

This supporting structure (32, 33, 34) allows the axes of the formingrollers (8, 8′) to perform a rototranslational movement, in the verticalplane, inside the forming station 3 that allows a considerable freedomin positioning and orienting the rollers (8, 8′) of each pair, whilstalways keeping them in contact with each other, to adapt them to thediameter of the tube to be produced, as schematically indicated in FIG.5, which shows the position assumed by the two pairs in rollers (8, 8′)for three diameters of the tube 2 coming within the tubes 2 that can beproduced without replacing the forming rollers (8, 8′).

The sliding movements of the horizontal traverses 32 along the uprights31 and of the shoes 33 along the traverses 32 and the rotation of theunits 35 around the relative pivots 34 are of the same amplitude andopposite direction, take place along guides indicated schematically withdashed lines in FIG. 3 and are realised by means of activating means notdescribed herein because they are per se known and not explicitlyindicated in FIG. 3 for the sake of simplicity of the graphicrepresentation.

FIG. 3A shows diagrammatically, enlarged, the area of the first formingstation 3 comprising the two pairs of rollers (8, 8′), supported by theunits 35, which deform the outermost area of the strip of sheet metal 4.

FIG. 4 shows diagrammatically, enlarged, a pair of forming rollers (8,8′), realised according to the invention, belonging to the first formingstation 3; from FIG. 4 it can be seen that the profile of the lowerrollers 8′ is elliptical with a curvature decreasing from the outer edgeto the inner edge of the roller 8′, whereas the profile of the upperrollers 8 is elliptical with a curvature increasing from the outer edgeto the inner edge of the roller 8.

The ellipses to which the profiles of the rollers 8 and 8′ belong havebeen indicated with dashed lines in FIG. 4.

FIG. 5 shows diagrammatically, enlarged, the position assumed by the twopairs of forming rollers (8, 8′) of the first forming station 3 toproduce three tubes 2 of different diameter coming within the tubes 2that can be produced without replacing the forming rollers (8, 8′): theelliptical profiles of the rollers 8 and 8′ allow the radius ofcurvature of the outermost areas of the strip of sheet metal 4 to bemodified by modifying only the position and orientation of the rollers(8, 8′).

FIG. 6 shows diagrammatically a front view of one of the second formingstations 3′ of the machine 1, situated downstream of the first formingstation 3, from which it differs essentially in that the upper rollers8″ have a circular profile whose radius corresponds to the minimumradius of curvature (within the range of tubes 2 that can be producedwithout replacing the forming rollers 8′ and 8″) of the bent strip ofsheet metal 4 in correspondence of said second forming station 3′ and inthat the pairs of forming rollers (8′, 8″) belonging to the secondforming stations 3′ deform the inner part of the strip of the sheetmetal 4.

The pivots 34 and the units 35, seen better in FIG. 6 a, have not beendesignated in FIG. 6 with the corresponding reference numerals for thesake of clarity of the graphic representation.

FIG. 6 a shows diagrammatically, enlarged, a pair of forming rollers(8″, 8′), realised according to the invention, belonging to a secondforming station 3; from FIG. 6 a it can be seen that the profile of thelower rollers 8′ is elliptical with a curvature decreasing from theouter edge to the inner edge of the roller 8′, whereas the profile ofthe upper rollers 8″ is circular.

FIG. 7 shows diagrammatically, enlarged, the position assumed by the twopairs of forming rollers (8′, 8″) of the second forming station 3′ ofFIG. 6 to produce the three tubes of different diameter of FIG. 5: theelliptical profile of the lower rollers 8′ allows the radius ofcurvature of the inner part of the strip of sheet metal 4 to be modifiedby modifying only the position and orientation of the forming rollers 8′and 8″.

The amplitude of the rototranslational movements permitted to theforming rollers (8, 8′, 8″) by the supporting structure (32, 33, 34) andthe particular profiles of the forming rollers (8, 8′, 8″) allow therange of values of the diameter of the tubes which can be producedwithout having to replace the forming (8, 8′, 8″) to be increased withrespect to machines of the prior art.

Moreover, from the foregoing description it is obvious that, in themachine of the present invention, the strip of sheet metal 4 is notdeformed by pairs of forming rollers (8, 8′, 8″) having matchingprofiles: this represents an obvious feature able to differentiate themachine of the present invention from machines of the prior artincluding that described in European patent EP 1 393 830.

FIG. 8 shows diagrammatically a front view of one of the containmentstations 12 situated downstream of the forming stations 3 and 3′.

This station 12, symmetrical with respect to the midline, consists oftwo guides 81, fixed to uprights 31, each of which allows translationalong an inclined axis of a shoe 82 which supports an idle roller 83,having a concave profile, which guides and supports the strip of sheetmetal 4 between two adjacent forming stations (3, 3′).

The containment stations 12 can be omitted without departing from thescope of the invention.

The upper part of each rollers 83 presents a protruding disc element 84(seen better in FIG. 8 a, which shows diagrammatically an enlargeddetail of the containment station 12), which protrudes with respect tothe body of the roller 83 to contain the edge 6 of the strip of sheetmetal 4.

FIG. 9 a shows diagrammatically a front view (FIG. 9 a) and a side viewsectioned along the plane F-F of FIG. 9 a (FIG. 9 b) of a finishingstation 5 belonging to the machine 1, which differs from the formingstations (3, 3′) previously described essentially in that each of theunits 35 carries a forming roller 91 acting on the outer surface of thestrip of sheet metal 4 bent to form the tube 2 and in that it furthercomprises a roller 92, the position of which between the edges 6 of thestrip of sheet metal 4 forming the tube 2 is adjustable by means of alever 93 operated in a per se known manner.

The units 35 and the rollers 91 and 92, seen better in FIG. 9 c, havenot been designated with the corresponding reference numerals in FIG. 9a for the sake of clarity of the graphic representation.

The forming rollers 91 have a concave profile, with a constant curvatureequal to the maximum value of the curvature presented by the strip ofbent sheet metal 4 in correspondence to the finishing station 5 duringproduction of one of the tubes 2 that can be produced without replacingthe forming rollers (8, 8′, 8″) of the forming stations (3, 3′); theroller 92 has a convex V-shaped profile.

In FIG. 9 b the strip of sheet metal 4, one of the forming rollers 91,the roller 92 inserted in the strip of sheet metal 4 and the lever 93which adjusts the position of the roller 92 can be seen.

FIG. 9 c shows diagrammatically an enlarged detail of the finishingstation 5 of FIG. 9 a, where the forming rollers 91 acting on the outersurface of the strip of sheet metal 4 bent to form the tube 2 and theroller 92 situated between the edges 6 of the strip of sheet metal 4 canbe seen better.

Without departing form the scope of the invention, a person skilled inthe art can make to the above described machine with variable linearstructure all the modifications and improvements suggested by normalexperience and/or by the natural evolution of the art.

1. A machine (1) for the continuous formation of tubes (2) including, inseries between each other, forming stations (3, 3′) able toprogressively bend a strip of sheet metal (4) and at least one finishingstation (5) able to further bring together the edges (6) of the bentstrip of sheet metal (4) in view of the final welding, each formingstation (3, 3′) including two pairs of idle forming rollers (8, 8′, 8″)able to carry out rototranslational movements of the same extent but inopposite directions, characterized in that: the profile of the lowerrollers (8′) of each forming station (3, 3′) is elliptical with adecreasing curvature from the outside edge to the inside edge of saidroller (8′); the profile of the upper rollers (8) of the first formingstation (3) is elliptical with increasing curvature from the outsideedge to the inside edge of said roller (8); the profile of the upperrollers (8″) of the forming stations (3′) subsequent to the first one(3) is circular.
 2. The machine (1) as in claim 1, characterized in thatthe at least one finishing station (5) includes four idle formingrollers (91), having a concave profile with a constant curvature, ableto carry out movements of the same extent and direction according to 90°axes.
 3. The machine (1) as in claim 1, characterized in that the radiusof the circular profile of the upper rollers (8″) of each formingstation (3′) subsequent to the first one (3) corresponds to the minimumradius of curvature of the bent strip of sheet metal (4) incorrespondence of said forming station (3′) subsequent to the first one(3).
 4. The machine (1) as in claim 1, characterized in that eachforming station (3, 3′) and at least one finishing station (5) includetwo vertical uprights (31) that support two horizontal traverses (32)sliding along the uprights (31), along each of said traverses (32)sliding two shoes (33), on each of which is present a pivot (34) thatacts as a fulcrum for the rotation of a unit (35) that carries one ofthe forming rollers (8, 8′, 8″; 91).
 5. The machine (1) as in claim 1,characterized in that the pairs of forming rollers (8, 8′) belonging tothe first forming station (3) deform the outermost areas of the strip ofsheet metal (4) and in that the pair of forming rollers (8′, 8″),belonging to the forming stations (3′) subsequent to the first one (3),deform the inner part of the strip of sheet metal (4).
 6. The machine(1) as in claim 1, characterized in that it also includes containmentstations (12), each of which is situated after a forming station (3,3′).
 7. The machine (1) as in claim 6, characterized in that eachcontainment station (12) includes two guides (81), fixed to the uprights(31), each of which allows the translation according to an inclined axisof a shoe (82) that carries a roller (83), having a concave profile,able to guide and to support the strip of sheet metal (4) between twoadjacent forming stations (3, 3′).
 8. The machine (1) as in claim 7,characterized in that the upper part of each roller (83) presents a discelement (84), protruding from the body of the roller (83), able tocontain the edge (6) of the strip of sheet metal (4).
 9. The machine (1)as in claim 4, characterized in that each of the units (35) of at leastone finishing station (5) carries a forming roller (91) acting on theouter surface of the strip of sheet metal (4) bent to form the tube (2)and in that it also includes a roller (92) and a lever (93) able toadjust the position of the roller (92) between the edges (6) of thestrip of sheet metal (4) forming the tube (2).
 10. The machine (1) as inclaim 9, characterized in that the forming rollers (91) have a concaveprofile, with a curvature constant and equal to the maximum value of thecurvature presented by the bent strip of sheet metal (4) incorrespondence of the finishing station (5) during the production of oneof the tubes (2) which are producible without replacing the formingrollers (8, 8′, 8″) of the forming stations (3, 3′) and in that theroller (92) has a convex V-shaped profile.